Movement of transposable elements contributes to cichlid diversity.

Area of Science:

• Evolutionary Biology
• Genetics
• Ichthyology

Background:

• African cichlids are key models for speciation research.
• Genetic variation underlying cichlid phenotypic diversity, especially visual sensitivity, remains challenging to pinpoint.
• Opsin gene expression drives significant spectral shifts in cichlid vision.

Purpose of the Study:

• To identify the genetic variants responsible for cichlid phenotypic variation.
• To investigate the role of transposable elements (TEs) in driving regulatory variation and speciation in African cichlids.

Main Methods:

• Mapping expression quantitative trait loci (eQTL) in intergeneric crosses of Lake Malawi cichlids.
• Analyzing the evolutionary history and genomic location of identified genetic variants (indels).
• Correlating transposable element (TE) movement with opsin expression variation.

Main Results:

• Identified four causative genetic variants as indels in gene promoters.
• Demonstrated these indels originate from transposable element (TE) movement.
• Found these TE-driven indels are endemic to Lake Malawi cichlids, indicating recent TE activity.
• Observed convergent TE movement at similar genomic locations, suggesting predisposed insertion sites.
• Linked increased TE mobility to interspecific hybridization and disrupted TE suppression mechanisms.

Conclusions:

• Transposable elements (TEs) are significant drivers of regulatory variation in African cichlids.
• TE activity facilitates rapid phenotypic change and may accelerate speciation.
• Hybridization events could enhance TE mobility, linking hybridization to accelerated regulatory evolution.